“A completely effective solution for clamping complex aircraft parts was missing, or at the very least needed much improvement,” observes Ana Pascual, technical manager of the EU-funded TGRIP project. The requirements needed to achieve effective clamping remain unmet. What’s more, clamping technologies can’t entirely meet these requirements because of limitations. After analysing clamping market needs, the project team came up with an alternative solution called F-GRIP by using reversible adhesives. “Finding the correct adhesive was challenging for two reasons,” notes Pascual. First, it must provide very strong adhesion to firmly secure raw materials and withstand severe machining conditions, even for demanding materials like titanium. Second, the final part has to be released after machining, so the adhesive needs to easily unstick.
Generating unrivalled clamping and adhesion forces
Since this material didn’t exist in the adhesive market, team members developed a specific polymeric adhesive that provides high adhesion (1 000 N/cm2) and the ability to unstick by using temperature. The innovation consists of a custom-made clamping fixture where the adhesives are placed and a temperature control system. Temperature control enables sticking and unsticking all types of materials with a high clamping force. Since small pressure has to be applied to the adhesive to obtain such high force, F-GRIP is able to firmly clamp without damaging or deforming the part. Moreover, the clamping is carried out only from one side of the part so it doesn’t compromise areas to be machined. The adhesive formulation is processed in solid round disks 10-30 mm in diameter and 1 mm thick. They are easy to manipulate and can also be recycled. The eco-friendly solution’s clamping force is 10 times greater than vacuum technologies. Unlike magnetic systems, it can clamp all materials. The technology can clamp both flat and curved surfaces, which is very difficult or impossible with other clamping systems. In addition, it can clamp more than one side of a part, something that can’t be done with mechanical jaws. Furthermore, it doesn’t damage or deform parts, and it can be applied to a wide range of materials and shapes. The patented F-GRIP will provide important benefits for the clamping stage during the manufacture of high-value parts like fuselage structures or engine parts. It’s capable of clamping new parts that are impossible with current technologies because of their complex geometries. The technology can reduce the number of clamping operations, increase machining stresses that are in some cases limited by inefficient clamping, improve the quality of the final machined part in terms of accuracy and finish surface, as well as decrease the number of defective pieces generated in the machining process due to unsuitable clamping.
Scaling up F-GRIP manufacturing and business
Project partners successfully validated the F-GRIP technology. They designed and fabricated several demonstrators for the serial production of workpieces like aircraft turbine blades, titanium aircraft engine parts and thin aluminium parts for cockpits. “Based on feedback, potential customers envision F-GRIP as a genuine solution for their future products,” admits Pascual. “To make the turnkey solution truly unique, the adhesive and clamping fixture requirements were adjusted to market needs.” The consortium built a pilot plant to manufacture its own adhesive with a production capacity of about 150 kg annually. It analysed a large plant to determine how an industrial adhesive manufacturing facility can respond to future demand. Lastly, F-GRIP presentations at key trade shows in Europe resulted in over 200 potential customer contacts.
TGRIP, clamping, adhesive, F-GRIP, aircraft, machining, clamping system, clamping fixture, aircraft part